avahi: fix error at boot time for avahi-daemon.service

The following error messages appear now and then at boot time.

  avahi-daemon/chroot.c: open() failed: No such file or directory
  Failed to open /etc/resolv.conf: Invalid argument

The problem is about /etc/resolv.conf. In Yocto's systemd based
systems, it's a symlink to /etc/resolv-conf.systemd which in turn
is a symlink to /run/systemd/resolve/resolv.conf. The systemd-resolved
service handles creation of /run/systemd/resolve/resolv.conf file.

So if avahi-daemon is started before systemd-resolved, the error messages
appear.

Fix this problem by making avahi-daemon start after systemd-resolved.

(From OE-Core rev: 647db1d9eb65b225ffbb6953f796232026bfa935)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-connectivity/avahi/avahi_0.7.bb

@@ -3,6 +3,7 @@ require avahi.inc
 SRC_URI += "file://00avahi-autoipd \
            file://99avahi-autoipd \
            file://initscript.patch \
+           file://0001-Fix-opening-etc-resolv.conf-error.patch \
            "
 
 inherit update-rc.d systemd useradd

meta/recipes-connectivity/avahi/files/0001-Fix-opening-etc-resolv.conf-error.patch

@@ -0,0 +1,40 @@
+From 78967814f5c37ed67f4cf64d70c9f76a03ee89bc Mon Sep 17 00:00:00 2001
+From: Chen Qi <Qi.Chen@windriver.com>
+Date: Wed, 20 Jun 2018 13:57:35 +0800
+Subject: [PATCH] Fix opening /etc/resolv.conf error
+
+Fix to start avahi-daemon after systemd-resolved.service. This is because
+/etc/resolv.conf is a link to /etc/resolv-conf.systemd which in turn is
+a symlink to /run/systemd/resolve/resolv.conf. And /run/systemd/resolve/resolv.conf
+is created by systemd-resolved.service by default in current OE's systemd
+based systems.
+
+This fixes errro like below.
+
+  Failed to open /etc/resolv.conf: Invalid argument
+
+In fact, handling of /etc/resolv.conf is quite distro specific. So this patch
+is marked as OE specific.
+
+Upstream-Status: Inappropriate [OE Specific]
+
+Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
+---
+ avahi-daemon/avahi-daemon.service.in | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/avahi-daemon/avahi-daemon.service.in b/avahi-daemon/avahi-daemon.service.in
+index 548c834..63e28e4 100644
+--- a/avahi-daemon/avahi-daemon.service.in
++++ b/avahi-daemon/avahi-daemon.service.in
+@@ -18,6 +18,7 @@
+ [Unit]
+ Description=Avahi mDNS/DNS-SD Stack
+ Requires=avahi-daemon.socket
++After=systemd-resolved.service
+ 
+ [Service]
+ Type=dbus
+-- 
+2.11.0
+